1. Field of the Invention
The application relates to communications systems and more particularly to wireless communications networks.
2. Description of Related Art
In current wireless networks, almost all multiple-cell, multiple-sector systems use some form of the well known frequency division duplex (“FDD”) mechanisms to run multiple radios in a physical location. The use of FDD helps to reduce the interference of the radio transmitters. Wireless Broadband Access (“WBA”) based systems have been designed to have operational characteristics that are indistinguishable from Cable or DSL methods of broadband access from the viewpoint of the customer. However, wireless systems are subject to substantial signal fading and interference.
Today almost all of the multiple-cell/multiple-sector systems use the well-known frequency division duplex (“FDD”) mechanisms to run multiple radios in a physical location. The use of FDD helps to reduce the interference between the radio transmitters. Two main usage methods for 3 sector applications are provided in FIG. 1. The first case 100 depicts an RF frequency usage pattern whereby each cluster comprises one base station site. Each base station site has three sectors in which each of the three sectors is assigned a unique RF channel. In the second case 102, an RF frequency usage pattern is depicted in which each cluster comprises one base station site and each base station site has three sectors with all sectors being assigned the same RF channel. In this case the FDD separation of radio transmitter is not being used. Interference in the first case 100 between the sectors using the same frequency is substantially less than in the second case. Therefore, the first case 100 configuration is currently preferred in most installations.
Inter-subscriber station interference can result in loss of bandwidth, signal corruption, signal disruption and increased power requirements in wireless networks. Another factor in conventional WBA systems is the substantial cost of the overall system and the cost and impact of upgrading as user demands change. The general method used today is to use a separate frequency for the upgrades. One example to this upgrade is the case of IEEE 802.16. There are two versions of IEEE 802.16 widely adopted today, one version being OFDM based, and the other OFDMA based. In deployments today if OFDM is deployed the service providers must need to allocate a new frequency to deploy OFDMA or vice versa. In the current economic situation the frequency is as valuable—sometimes more valuable than the WBA systems deployed—and this is not an attractive solution. When compounded with the fact that most of the service providers are not even sure which services they offer will be accepted by the users the case of allocating/buying a new frequency is not an attractive option.